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I set up a CentOS6-XEN4-Server according to these instructions.

Now I want to set up bridges - first manually:

brctl addbr test - but this fails with:

"add Bridge failed: Package not installed"

Googling about that I tried to manually modprobe bridge which triggers an error that is caused-according to dmesg by:

bridge: Unknown symbol ipv6_dev_get_saddr (err 0)

modinfo bridge reveals that the bridge-modules depends on stp,llc and ipv6.

Great. I do not want IPv6, I do not need IPv6 and have blacklisted IPv6.

  1. Is there any way to get brctl running without enabling IPv6?

  2. Why is that depency there at all?

Update 2014-05-14

I found this to be a general CentOS 6/RH 6 problem. It also applies to the bonding module.

The accepted answer describes the root-cause - so this problem will also arise on comparable kernel-versions and is not restricted to CentOS/RedHat/Scentific Linux 6.

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Disabling IPv6 is a serious mistake. You do need it, if not today (or even years ago!) then very soon. –  Michael Hampton Jan 14 at 16:28
    
@MichaelHampton on directly internet connected systems maybe. On intranet, linux-systems - nope. –  Nils Jan 14 at 21:56
    
You need it even more on internal systems! Perhaps you don't yet understand IPv6... –  Michael Hampton Jan 14 at 21:58

1 Answer 1

up vote 1 down vote accepted

it has been discussed on the kernel ML and the conclusion was that users shouldn't disable ipv6 anymore.

quoted from https://bugzilla.redhat.com/show_bug.cgi?id=685053

The workaround for this situation is to not blacklist the ipv6 module, but rather set its disable_ipv6 module option. That way the code gets loaded, but no ipv6 functionality is registered with the kernel so user space can't accesses it.

Update 2014-05-14:

The correct workaround seems to be:

  1. Un-blacklist ipv6 and net-pf-10
  2. create /etc/modprobe.d/ipv6.conf with the following content:

    options ipv6 disable_ipv6=1

share|improve this answer
    
Excellent reference - although I would not name RH-bugzilla a kernel-ML. Interesting option for the IPv6-module. –  Nils Jan 14 at 21:59
    
i was actually referring to another ML (LKML) where this topic has been discussed as well. –  alxgomz Jan 14 at 23:45
    
BTW: There seems to exist the same problem with the bonding-module. –  Nils May 13 at 15:01

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